.577-450 and .471 diameter bullets

[GunsNotPuns]

This is going to be a bit of a Captain Obvious question but snow shoveling has addled my brain.

So I no longer have access to the 480 grain cast bullets I was using to handload .577/450 -- ones I rather liked -- so I had to turn to Jet Bullets. I bought some 480 grain from them that were billed as appropriate for that calibre but they are .471", rather than the .460" I was using before. Long story short, seating the bullets resulted in a split neck or two from the brass (granted it was old brass with an unknown number of firings).

Am I out to lunch and .471" is too large for what I'm doing? The specs call for a .450"-ish inner rim diameter and all...

 

[catnip]

Mine are paper patched to .469/.470 so I don't see .471 as being out of line. There are some pretty generous throats and bores in those old rifles. You can always size those bullets down to what fits yours. ...catnip

 

[antiqueguy]

Anneal your necks and shoot away the martini has a long throat and it shouldn’t be too much of a problem. Groove diameter on these is around .467 or so usually on British martinis anyway.

 

[GunsNotPuns]

Thanks for the answers. I did put a round in the chamber this morning just as a check and I noticed that they were a tight-ish fit with still about 1/2 centimetre left to go. I decided to withdraw at that point -- didn't feel like pounding out a round from the chamber.

 

[Andy]

For the Martini-Henry, I use the Lee 476-400-RF sized down to 0.470" with a custom sizer. You lose more lube capacity than I like when sizing it down that much, but it worked well:

 

[antiqueguy]

For the Martini-Henry, I use the Lee 476-400-RF sized down to 0.470" with a custom sizer. You lose more lube capacity than I like when sizing it down that much, but it worked well:

I have always wondered about that bullet I though sizing it would cause issues.

 

[dakotamar]

For the Martini-Henry, I use the Lee 476-400-RF sized down to 0.470" with a custom sizer. You lose more lube capacity than I like when sizing it down that much, but it worked well:

would alox be a better way to lube it?

 

[Andy]

would alox be a better way to lube it?

That's what I used. One application before sizing and one after.

 

[antiqueguy]

If one uses a lube cookie in the case neck and lubes the bullet in some way I bet it’s a non issue.

 

[howard2]

I am no expert but have friends in the black powder silhouette rifle sport. The take away knowledge that I learnt from them regarding this years ago was: slug your bore, obtain mold just a little oversized, pan lube or run through lubsizer for lube with no sizing needed.

 

[antiqueguy]

I am no expert but have friends in the black powder silhouette rifle sport. The take away knowledge that I learnt from them regarding this years ago was: slug your bore, obtain mold just a little oversized, pan lube or run through lubsizer for lube with no sizing needed.

The biggest issue with the martini is it’s not like a lot of other guns. The throat is bigger than the muzzle and it’s 13 or so inches long. The military cartridges were paper patched to .462 or so but these shoot the best with a .468 to .470 diameter bullet. no need to reinvent the wheel as lots of guys have went down the road of playing with these guns trying to make them shoot.